Promax/FF ?

[mercrazy]

I have a promax and ff block laying side by side.
the only difference I see is size of dump holes.
chests look identical and ports measure same best I could measure.
there is a little molding flash at edges of rod slots on the ff.
is there a difference behind the liner?
am I missing something?
I don’t have promax front half to compare.

[25two.stroke]

am I missing something?
No.
Front half is 7 petal on promax, 4/5 on FF

[skialot2]

Promax 200 has a 4 petal front with duel stage reeds. FF has standard metal reeds. ProMax 225 has 7 petal duel stage reeds

544881 544882

[LakeFever]

Look close at the exhaust port on the sleeve. The 225 promax should have a chamfer and the FF does not. The front half and the dump hole are the biggest mechanical differences though. The ecu is also tuned to run more rpm with the promax as well

[mercrazy]

Look close at the exhaust port on the sleeve. The 225 promax should have a chamfer and the FF does not. The front half and the dump hole are the biggest mechanical differences though. The ecu is also tuned to run more rpm with the promax as well
Yes I noticed the chamfer. This ff does have a chamfer about half as much as promax.
ill be running carbs for this build. Wish I could find a 7 petal front.

[LakeFever]

yeah seven petal front halves are always in demand. They do come up for sale though just have to be patient and willing to pay is all. From what I’ve figured the seven petal is worth 25 ponies up top vs the smaller fronts

[KIRCHNER]

what are duel stage reeds?

[mercrazy]

what are duel stage reeds?
They have 2 layers of fiber, one laying on top of the other. Supposedly the top layer opens easier at lower rpm and the bottom layer opens at higher rpm. That’s the explanation I got. Someone in the business says it’s snake oil and you only need one layer. I don’t know.

[skialot2]

They have 2 layers of fiber, one laying on top of the other. Supposedly the top layer opens easier at lower rpm and the bottom layer opens at higher rpm. That’s the explanation I got. Someone in the business says it’s snake oil and you only need one layer. I don’t know.

This is exactly correct. I believe the theory is that you get better velocity at lower RPM with the smaller opening first stage of the reed. Then at higher RPM the second stage opens allowing more airflow overall. But in my opinion when the first stage opens you lose the sucking power to open the second stage. In fact I was told by someone they glued down the larger second stage petal on Boyeson duel stage reeds and could not tell the difference in testing

[LakeFever]

Yeah I’m going to branch off here and suggest the two stage reeds is just silly. Your basically asking for a second seal area to be as close to perfect as possible and your taking an already lightweight part and giving it twice the areas to break. Maybe they make more power I can’t say but I won’t be running them in my builds. The only real noticeable difference I’ve ever had with reeds in other motors was getting a good seal on the block. Seems to make my stuff work best

[David - WI]

yeah seven petal front halves are always in demand. They do come up for sale though just have to be patient and willing to pay is all. From what I’ve figured the seven petal is worth 25 ponies up top vs the smaller fronts

The stock 225 ProMax makes 245hp... so that "theory" is just a wild-ass guess.

Jay Smith claimed the 200 ProMax had an intake restriction built in that cost it 30hp... besides the reed difference.


The smaller HP motors have a restriction of the intake charge path to reduce HP. I modify these vapor paths on the blocks to mirror the higer HP 225's and can put another 25 30 HP very easily.
https://www.screamandfly.com/showthread.php?252372-What-is-the-difference-in-the-year-make-of-Mercury-ProMax-motors&p=2334992#post2334992

If the 200PM without the extra intake restriction makes 230 horsepower and the 225PM makes 245hp, then at best the 7-petal intake would be good for 15hp.

Odds are that the stock 200PM is over 200hp to begin with, so without the extra intake restriction it's probably (210hp + 30hp) 240hp - meaning the 7-petal front is worth 5hp or less.

[LakeFever]

The stock 225 ProMax makes 245hp... so that "theory" is just a wild-ass guess.

Jay Smith claimed the 200 ProMax had an intake restriction built in that cost it 30hp... besides the reed difference.


https://www.screamandfly.com/showthread.php?252372-What-is-the-difference-in-the-year-make-of-Mercury-ProMax-motors&p=2334992#post2334992

If the 200PM without the extra intake restriction makes 230 horsepower and the 225PM makes 245hp, then at best the 7-petal intake would be good for 15hp.

Odds are that the stock 200PM is over 200hp to begin with, so without the extra intake restriction it's probably (210hp + 30hp) 240hp - meaning the 7-petal front is worth 5hp or less.


There certainly is a lot of varying opinions on all this in the archives here. All I can say for sure is I’ll know first hand if these perform or not. It’s not really rocket science here. We are pumping air. The more air you pump the more power you make. The cubic inches limit the volume you can move so the only way to move more is increase rpm or increase cubic inches. My current motor with the four petal is choking somewhere. I began a thread trying to figure this out but anyone who knows isn’t spilling the beans so this next go around I’m stuffing everything on it I can to improve the airflow and raise the rpm. Whatever the results end up I’ll post about

[mercrazy]

My current motor with the four petal is choking somewhere. I began a thread trying to figure this out but anyone who knows isn’t spilling the beans so this next go around I’m stuffing everything on it I can to improve the airflow and raise the rpm. Whatever the results end up I’ll post about
Did you enlarge the exhaust dump holes?

[LakeFever]

Yes I copied a promax block as close as I could. I’m even running a promax ecu it’s just the front half that is different